Junction field effect transistors have many desirable properties which are useful in switching applications. However, the relatively high capacitance associated with large junction field effect transistors has limited their usefulness for high speed switching applications.
Accordingly, a principal object of the present invention is to increase the turn-on and turn-off speeds of large size junction field effect transistor switches, without the need for large idle currents present in the switching or control circuitry for the big switch JFET.
In integrated circuits, when a junction field effect transistor is used as a switch, and an analog voltage is applied across the source and drain electrodes of the JFET to be switched, there is a significant danger that heavy fault currents will flow, in the event that the signals applied to either the source or the drain electrode of the switch JFET exceed the positive or the negative supply voltages. Accordingly, another important object of the present invention is to prevent the flow of heavy fault currents when such voltages are applied to the source or drain electrodes of the big switch JFET.